This drug is a calcium ion influx inhibitor (calcium channel blocker) which is used to treat hypertension (high blood pressure), angina (chest pain) and irregularities in the heartbeat.
It has been sold under the trade names Calan and Isoptin.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.